For reeling paper reels it is common to use two systems to maintain continuous production in the reel-up, namely a primary system, having a pair of pivotable primary arms with gripping devices to receive an empty reeling drum, and a secondary system, which receives the reeling drum from the primary system once an initial number of turns of the paper web have been wound onto the reeling drum. The secondary system usually has either a pair of secondary arms or a pair of secondary carriages, which, as the diameter of the paper reel increases, are pivoted or linearly displaced, depending on the case, along a pair of mutually parallel stand members, on which a driven surface winding drum is rotatably arranged, over which the paper web runs. The primary arms place the reeling drum to abut the surface winding drum to initiate reeling of the web. Thereafter, the primary arms convey the reeling drum along the surface winding drum down to two rails, along which the reeling drum, rotatably carried by its bearing housings, is displaced during the continued reeling of the web. It is important that a certain linear load is maintained against the surface winding drum and that the paper reel, during its growing, is evenly reeled without creases and folds arising in the layers, especially the inner layers, which otherwise must be discarded. The linear load varies throughout the reeling-up operation in magnitude as well as direction and depends mainly on the three variables applied load, weight increase of the growing paper reel, and current location of the paper reel along the envelope surface of the surface winding drum. The location relative to the surface winding drum causes the linear load to vary, as the paper reel is pressed against the envelope surface along a contact line, which is shifted downwards in an arc-shaped movement along the envelope surface, whereby a horizontal as well as a vertical force component arises, the magnitudes of which vary mutually throughout the entire movement. The linear load is affected negatively also during the transfer of the reeling drum from the primary system to the secondary system, as an exchange must take place between the separate gripping members of the two systems and, with central drive, between two separate drive means as well, whereby a temporary increase in pressure arises. To optimize the reeling-up operation, the linear load must be kept within carefully determined maximum and minimum values throughout the entire reeling-up process. To reduce the negative effects of the described variations in the linear load between the growing paper reel and the surface winding drum, arrangements with cam steerings and/or power cylinders by the primary arms to regulate the linear load in the nip have been tested. Thus, U.S. Pat. No. 3,614,011 describes a reel-up with two primary arms, which each have a loading device outside the reeling drum to regulate the applied load, which loading device comprises a power cylinder and a holding hook displaceable along the primary arm by means of the power cylinder. Each loading device co-operates with an unloading device, comprising a lower, manoeuvrable cam track, arranged at each end of the surface winding drum of the reel-up. The reeling drum is supported on the cam tracks and conveyed along the curved surfaces of the same down to a pair of rails, where two secondary arms assume control of the paper reel. Each cam track is pivotable about a shaft by means of a power cylinder to be able to regulate the linear load to some extent while the paper reel is growing against the surface winding drum. The linear load in the nip is thus regulated by the power cylinders of the loading devices, through the displacement of the locking hooks, as well as by the power cylinders of the unloading devices, through the adjustment of the cam tracks. U.S. Pat. No. 4,634,068 describes a reel-up, in which it is sought to control the variation of the linear load. Each primary arm comprises a loading device with a power cylinder, which controls an upper locking hook displaceable along the primary arm, and an unloading device, arranged at the primary arm and having a lower support with an unloading cylinder, arranged to relieve the nip of the increasing weight of the paper reel. In the known reel-ups described above, the control of the linear load must be performed by two completely separate, but yet necessarily mutually co-operating, devices, of which the loading device alone regulates the applied load, while the unloading device regulates the unloading of the weight of the reeling drum and the increasing weight of the growing paper reel. This makes it very difficult to control the linear load in an optimal way. A further problem with both these known reel-ups is that their primary arms have gripping devices with fixed or substantially fixed lower holders for the reeling drum. The diameter of the paper reel can thus only be permitted to increase to a certain pre-determined maximum limit before the paper reel lifts the reeling drum from said lower holders. To be able to reel more paper onto the reeling drum while it is still held by the primary arms, the displaceable upper locking hook and the fixed lower holder or cam track have, in some reel-ups, been replaced by a gripping device with two pivotable gripping parts, consisting of an upper locking hook and a lower support arm, both being journalled to the primary arm about separate pivoting shafts. As the diameter of the paper reel increases, the locking hook and support arm are pivoted out from the envelope surface of the surface winding drum. The reeling drum is thereby undesirably rotated within the gripping device, which rotation is caused by the locking hook and support arm being displaced in parallel relative to the surface winding drum whilst simultaneously being pivoted about their respective pivoting shafts, journalled a distance from each other.